JP7064355B2 - Method for manufacturing polyolefin multilayer sheet or film - Google Patents

Description

The present invention relates to a method for producing a polyolefin multilayer sheet or film.

It is known that the sheet or film has a multi-layer structure in order to impart excellent functions. For example, polyolefins such as polypropylene are useful as food containers because they have excellent physical properties and are also excellent in hygiene, but in order to improve the impact resistance improvement at low temperatures, the containers are multi-layered. It has been proposed to have a structure (for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 10-157033 Japanese Unexamined Patent Publication No. 2002-348421

The inventors have come up with the idea that if the thickness of a particular layer can be made thinner, it may be possible to impart even higher functionality to the sheet or film. In general, when a multilayer sheet or film is manufactured through a coextrusion step, the layer can be made thinner by lowering the discharge amount of the molding machine forming the specific layer. However, when forming an extremely thin layer, the discharge amount must be extremely reduced, and it is difficult to form a thin layer under conventional molding conditions, or even if it can be formed, it is difficult to achieve a uniform thickness. there were. In view of such circumstances, the present invention is a polyolefin multilayer sheet including an outer layer having a uniform thickness of 1/40 to 1/100 with respect to the total thickness and a uniform thickness of 2 to 50 μm, and a core layer thicker than this. Or the subject is to provide a film.

The inventors have found that a polyolefin multilayer sheet or film having an outer layer having a uniform thickness of 2 to 50 μm can be produced by adopting special molding conditions, and completed the present invention. That is, the above problem is solved by the following invention.
[1] A polyolefin multilayer sheet or film having an outer layer and a core layer and satisfying the following i) and ii):
i) The thickness of the outer layer is 1/40 to 1/100 of the total thickness and 2 to 50 μm. Ii) The core layer is thicker than the outer layer by the manufacturing method.
The steps comprising coextruding the outer layer and the core layer to form a polyolefin multilayer sheet or film satisfying i) and ii).
The extruder for forming the outer layer in the coextrusion step includes a feed zone and a compression zone from the upstream.
The temperature T (° C.) of the feed zone satisfies the relationship of the equation (1).
Tm-50 ° C ≤ T ≤ Tm-10 ° C ... (1)
(Tm is the melting point (° C.) of the raw material polyolefin)
Production method.
[2] The production method according to [1], further comprising a step of secondary processing the polyolefin multilayer sheet or film obtained in the coextrusion step so as to satisfy the above i) and ii).
[3] The production method according to [1] or 2], wherein the outer layer contains polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin.
[4] Polypropylene composition having the following core layer:
As the component (1), it is a blend of a propylene homopolymer and a propylene copolymer containing a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin, and the weight ratio of the two is 10 to 97. : A blend of 90 to 3 and having a comonomer content of 3% by weight or less in the blend, and 60 to 90% by weight of ethylene as the component (2) and one or more kinds of C3 to C10-α-olefins. Includes an ethylene copolymer, which consists of a copolymer of
The following (i) to (iii) are provided. (I) The weight ratio of the component (1): component (2) is 60 to 90:40 to 10.
(Ii) MFR (230 ° C., load 2.16 kg) 1.0 to 10 g / 10 minutes (iii) XSIV (extreme viscosity of xylene soluble content) 0.5 to 2.0 dl / g,
The production method according to any one of [1] to [3], which comprises.
[5] The manufacturing method according to [4], wherein the multilayer sheet or film includes three or more layers, and the outer layers are located on both outermost surfaces.
[6] The manufacturing method according to [5], wherein the multilayer sheet or film has a three-layer structure.
[7] The production method according to any one of [1] to [6], wherein the polypropylene composition has a phase structure in which the component (2) is dispersed in the component (1).
[8] The comonomer in the component (1) is ethylene, and the comonomer is ethylene.
The production method according to any one of [4] to [7], wherein the α-olefin in the component (2) is propylene or butene-1.
[9] The production method according to any one of [3] to [8], wherein the comonomer in the polypropylene is ethylene.
[10] A multilayer sheet or film obtained by the production method according to any one of [1] to [9] above.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polyolefin multilayer sheet or film having an outer layer having a uniform thickness of 1/40 to 1/100 with respect to the total thickness and a uniform thickness of 2 to 50 μm, and a core layer thicker than the outer layer. ..

It is a figure which shows one aspect of a screw structure.

In the present invention, the sheet is a flat member (leaf-shaped member) having an overall thickness of 200 μm or more, and the film is a flat member (leaf-shaped member) having an overall thickness of less than 200 μm. Sheets or films are collectively referred to as "sheets, etc."

1. 1. Manufacturing Method The present invention includes a step of coextruding and forming an outer layer having a specific thickness and a polyolefin multilayer sheet having a core layer thicker than the outer layer. In the coextrusion process, molten resin is formed using a plurality of extruders, each molten resin is passed through a multilayer feed block, a multilayer manifold, or the like to form a multilayer structure, which is cooled and solidified to form a molded product. This is the manufacturing process. Hereinafter, the co-extrusion process will be described.

(1) Step of Forming Outer Layer In the present invention, the outer layer is formed by using an extruder having a screw configuration including a feed zone and a compression zone from the upstream. The raw material resin input side of the extruder is called the upstream, and the die side is called the downstream. FIG. 1 shows one aspect of the screw configuration. In FIG. 1, 1 is a raw material resin input port, 2 is a feed zone, 3 is a compression zone, and 4 is a weighing zone.

The feed zone is a zone in which the raw material resin supplied from the raw material resin input port is transferred downstream in a nearly solid phase state, and is also called a solid phase zone. In the present invention, the temperature T (° C.) of the zone satisfies the relationship of the formula (1).
Tm-50 ° C ≤ T ≤ Tm-10 ° C ... (1)
In the formula (1), Tm is the melting point (° C.) of the raw material resin (raw material polyolefin). The lower limit of T is preferably Tm −45 ° C., more preferably Tm −40 ° C. The upper limit of T is preferably Tm-20 ° C. When T is lower than Tm-50 ° C., the resin is not melted and sheet molding becomes difficult. When T is higher than Tm-10 ° C., the thickness of the outer layer fluctuates greatly in the width direction of the sheet or the like, and appearance defects such as uneven gloss occur as a whole and transparency deteriorates. Tm is the peak top temperature on the highest temperature side observed by the second scan of the raw material resin using DSC. The second scan is to heat and melt the raw material resin, cool it to crystallize it, hold it at room temperature for 5 minutes, and then heat it a second time for thermal analysis. Specifically, 1) the raw material resin is heated to a melting temperature (230 ° C.), held at that temperature for 5 minutes, cooled to 30 ° C. at a temperature lowering rate of 10 ° C./min, and held for 5 minutes, and then 2). Thermal analysis is performed by heating to 230 ° C. at a heating rate of 10 ° C./min. When polypropylene-based polyolefin is used as the raw material resin, T can be about 120 to 160 ° C. The length of the feed zone is appropriately adjusted, but assuming that the length from the raw material charging position of the screw to the downstream end is L, the feed zone is preferably a length of 0.15 L to 0.3 L.

The compression zone is a zone in which a resin in a solid phase state is heated and compressed to be in a molten state. The temperature T'in the zone is appropriately adjusted, but is preferably Tm or higher. Specifically, when polypropylene-based polyolefin is used as the raw material resin, T'can be set to about 210 to 240 ° C. The length of the compression zone is appropriately adjusted, but is preferably 0.65 L to 0.8 L. The compression zone may be provided with a so-called kneading zone that allows strength kneading. It is preferable that the compression zone and the feed zone are adjacent to each other.

The weighing zone is a zone for transferring the molten resin to the die. The temperature T "of the zone is appropriately adjusted, but is preferably Tm or more, and may be the same as T'. The length of the measuring zone is appropriately adjusted, but is 0.05 L to 0.2 L. It is preferable that another zone may be provided between the weighing zone and the compression zone, but it is preferable that the weighing zone and the compression zone are adjacent to each other.

The discharge amount of the extruder for the outer layer can be appropriately adjusted depending on the thickness of the outer layer and the size of the sheet or the like, but is preferably about 0.12 to 4.5 kg / hour, for example. Generally, the smaller the diameter of the extruder, the more stable the resin can be extruded even at a lower discharge rate. Making it smaller is not realistic. On the other hand, the extruder for the core layer has a diameter of 30 mmφ to 90 mmφ for industrial use. From the balance between the diameter of the extruder for the outer layer and the diameter of the extruder for the core layer, it is possible in principle to form an outer layer having a thickness of 1/40 to 1/100 of the total thickness. be. However, under the conventional molding conditions, the discharge amount of the extruder for the outer layer is set to be small, so that the discharge amount is not stable, the thickness variation becomes large in the width direction of the sheet, etc., and the appearance such as uneven gloss as a whole becomes large. As defects occur, transparency deteriorates. However, in the present invention, by setting the temperature of the feed zone to the above-mentioned temperature in the extruder for the outer layer, the resin can be efficiently transferred in the cylinder, so that the thickness is 1/40 to 1/100 of the total thickness. An outer layer having a thickness of 2 to 50 μm can be stably formed, and continuous production of transparent sheets and the like having a good appearance has become possible. If the thickness exceeds 50 μm, the impact resistance of the obtained polyolefin multilayer sheet or the like is lowered, and if it is less than 2 μm, stable formation of a thin outer layer becomes difficult and the transparency of the obtained polyolefin multilayer sheet or the like deteriorates. From this viewpoint, the upper limit of the thickness of the outer layer is preferably 40 μm or less, more preferably 35 μm or less, and further preferably 30 μm or less. The lower limit is preferably 4 μm or more, more preferably 8 μm or more, and further preferably 10 μm or more. The thickness ratio is preferably 1/40 to 1/95, more preferably 1/45 to 1/95.

The present invention achieves the thickness conditions i) and ii) by coextrusion. Therefore, the production method of the present invention may include other steps such as secondary processing as long as it includes the coextrusion step. The secondary processing will be described later.

The polyolefin multilayer sheet or the like of the present invention has a layer having a thickness of 1/40 to 1/100 and 2 to 50 μm (also referred to as a “thin-walled layer”) as an outer layer, and a thicker layer (“thick-walled layer”). ”) As a core layer. Therefore, the outer layer is located on the outside (surface side) of the core layer located at the center of the polyolefin multilayer sheet or the like. Therefore, when the polyolefin multilayer sheet or the like of the present invention has three layers, the two outer layers (thin-walled layers) are the outermost layers (outermost layers). When the polyolefin multilayer sheet or the like of the present invention has four or more layers, it is preferable that at least one thin-walled layer is the outermost layer (outermost layer). However, when the polyolefin multilayer sheet or the like of the present invention has two layers, the thin-walled layer is referred to as an outer layer and the thick-walled layer is referred to as a core layer for convenience.

(2) Step for Forming Core Layer The configuration and molding conditions of the extruder for forming the core layer are not particularly limited, the temperature may be a known temperature, and the discharge amount may be appropriately adjusted according to a desired thickness. In one aspect, the polyolefin multilayer sheet or the like of the present invention preferably has a three-layer structure of an outer layer / core layer / outer layer. In the case of such a three-layer structure, in the conventional technique, the thickness ratio is generally 1: "5 to 20": 1, but according to the present invention, the thickness ratio is 1: 1. "40-100": 1 can be set.

One or more intermediate layers may be further provided between the outer layer / core layer, and the configuration and molding conditions of the extruder forming the intermediate layer may be appropriately adjusted. The intermediate layer is preferably thicker than the outer layer and thinner than the core layer, and the specific thickness thereof is not limited, but may be, for example, 0.05 to 2 mm.

(3) Other Steps A polyolefin multilayer sheet or the like can be manufactured by laminating the molten resin obtained by the above-mentioned molding machine and cooling and solidifying the molten resin. The step of laminating may be as known, and for example, a known multi-layer feed block or multi-layer manifold can be used. The step of cooling and solidifying the molded product may be as known, and examples thereof include air cooling the molded product and placing the molded product on a chill plate or the like. When placed on a chill plate or the like, the thickness of the molded product can be appropriately adjusted by adjusting the take-up speed. The molded product thus obtained, that is, a polyolefin multilayer sheet or the like, is formed into a shape according to the application and can be used for various applications.

The polyolefin multilayer sheet or the like thus obtained can be used as the raw material, and further subjected to secondary processing such as vacuum forming, compressed air forming, vacuum forming and the like to adjust the thickness to a desired value as a stretched molded product. can. The secondary processing may be carried out so as to satisfy the thickness conditions i) and ii) of the original fabric, or the secondary processing may be carried out so as not to satisfy the thickness conditions i) and ii). However, considering the characteristics of the obtained polyolefin multilayer sheet or the like, it is preferable that the secondary processing is carried out so that the processed polyolefin multilayer sheet or the like satisfies the thickness conditions i) and ii). That is, the manufacturing method of the present invention may include a step of secondary processing the raw fabric so as to satisfy the thickness conditions i) and ii). In this case, the actual thicknesses of the outer layer and the core layer do not fluctuate, or even if they fluctuate, the thickness conditions i) and ii) are satisfied. The secondary processed product thus obtained is not necessarily leaf-shaped, but the polyolefin multilayer sheet or the like of the present invention also includes the secondary processed product.

2. 2. Polyolefin multilayer sheet, etc. The polyolefin multilayer sheet, etc. of the present invention is composed of polyolefin. Examples of the polyolefin used in the present invention include polypropylene, polyethylene, ethylene / propylene copolymer, ethylene / propylene / conjugated diene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, and ethylene. -Examples include 1-octene copolymer, propylene / 1-butene copolymer, propylene / 1-hexene copolymer, propylene / 1-octene copolymer and the like. The polypropylene may be any of homopolypropylene (propylene homopolymer), random polypropylene (propylene random copolymer), and block polypropylene. Here, the block polypropylene is also referred to as a heterophasic copolymer, a heterophasic polypropylene, an impact-resistant propylene polymer, or an impact-resistant polypropylene polymer, and contains a rubber component obtained by copolymerization or mixing. Refers to polypropylene. The polyethylene may be any of ultra-low density polyethylene, low density polyethylene, linear low density polyethylene, medium density polyethylene, and high density polyethylene. One type of polyolefin may be used alone, or two or more types may be used in combination. Among the above-mentioned polyolefins, polypropylene is preferable in that the effect of the present invention is particularly exhibited. All of these polyolefin multilayer sheets and the like are excellent in transparency and cold impact resistance, and are therefore useful as packaging materials, container materials, and particularly food containers. Since the thickness and position of each layer have already been described, the preferable materials constituting each layer will be described below.

(1) Outer layer The outer layer preferably contains polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin. In particular, it is preferable to contain a propylene homopolymer or a propylene random copolymer. The content of the comonomer in the propylene random copolymer may be 5.0% by weight or less, but preferably 4.0% by weight or less. If the amount of comonomer exceeds the upper limit, the manufacturing stability of the obtained sheet or the like is lowered. The lower limit of the content of the comonomer in the propylene random copolymer may be more than 0% by weight, but is preferably 0.1% by weight or more. The propylene homopolymer and the propylene random copolymer can be produced by a known method. Ethylene is preferable as the comonomer in the propylene random copolymer from the viewpoint of industrially inexpensive and stable distribution and relatively easy availability. The polypropylene preferably has an MFR of 1.0 to 10 g / 10 min (measured at 230 ° C. and a load of 2.16 kg). If the MFR exceeds the upper limit value, it is easy to draw down during molding, which makes it difficult to manufacture a sheet or the like. If it is less than the lower limit value, the load during molding becomes large and it becomes difficult to manufacture a sheet or the like.

A composition obtained by adding a crystal nucleating agent to a propylene homopolymer or a propylene random copolymer may be used for the outer layer. The crystal nucleating agent referred to here is an additive (transparent nucleating agent) used for controlling the size of the crystal component in the resin to be small and enhancing the transparency. The amount of the crystal nucleating agent is preferably 1.0 part by weight or less, more preferably more than 0 part by weight and more preferably 1.0 part by weight or less, and 0.05 to 0 parts by weight with respect to 100 parts by weight of the polymer. It is more preferably 5.5 parts by weight. If the amount of the crystal nucleating agent exceeds the upper limit, the effect of promoting the formation of crystal nuclei reaches a plateau, and the manufacturing cost simply increases, which is not realistic in the case of industrially mass production at low cost.

The crystal nucleating agent is not particularly limited, and those usually used in the art may be used, but nonitol-based crystal nucleating agents, sorbitol-based crystal nucleating agents, phosphate ester-based crystal nucleating agents, and triaminobenzene derivative-based crystals may be used. It is preferably selected from organic nucleating agents such as nucleating agents, carboxylic acid metal salt-based crystal nucleating agents, and xylitol-based crystal nucleating agents and rosin-based crystal nucleating agents. Examples of the nonitol-based crystal nucleating agent include 1,2,3-trideoxy-4,6: 5,7-bis-[(4-propylphenyl) methylene] -nonitol. Examples of the sorbitol-based crystal nucleating agent include 1,3: 2,4-bis-o- (3,4-dimethylbenzylidene) -D-sorbitol. Examples of the phosphoric acid ester-based crystal nucleating agent include phosphoric acid-2,2'-methylenebis (4,6-di-tert-butylphenyl) lithium salt-based crystal nucleating agent. Examples of the triaminobenzene derivative-based crystal nucleating agent include 1,3,5-tris (2,2-dimethylpropanamide) benzene and the like. Examples of the carboxylic acid metal salt-based crystal nucleating agent include sodium adipate, potassium adipate, aluminum adipate, sodium sebacate, potassium sebacate, aluminum sebacate, sodium benzoate, aluminum benzoate, and diparat. Examples thereof include aluminum-butyl benzoate, di-para-t-butyl benzoate titanium, di-para-t-butyl benzoate chromium, hydroxy-di-t-butyl benzoate aluminum and the like. Examples of the xylitol-based crystal nucleating agent include bis-1,3: 2,4- (5', 6', 7', 8'-tetrahydro-2-naphthaldehydebenzylidene) 1-allylxylitol, bis-1,3. : 2,4- (3', 4'-dimethylbenzylidene) 1-propylxylitol. The rosin-based crystal nucleating agent includes loginic acid such as pimalic acid, sandalakopimal acid, palastolic acid, isopimal acid, abietic acid, dehydroabietic acid, neoavietic acid, dihydropimalic acid, dihydroavietic acid, tetrahydroabietic acid, and calcium. It is a abietic acid metal salt compound or a abietic acid partial metal salt compound obtained by a reaction with a metal such as magnesium, and examples thereof include a abietic acid partial calcium salt. The above crystal nucleating agent may be used alone or in combination of two or more.

In addition, the polymers constituting the outer layer include antioxidants, chlorine absorbers, heat stabilizers, light stabilizers, ultraviolet absorbers, internal lubricants, external lubricants, antiblocking agents, antistatic agents, and antifogging agents. Usually used for olefin polymers such as agents, flame retardants, dispersants, copper damage inhibitors, neutralizers, plasticizers, foaming agents, bubble inhibitors, crosslinkers, peroxides, oil spreads and other organic and inorganic pigments. Conventional additives used may be added. The addition amount of each additive may be a known amount.

When a crystal nucleating agent and other additives are added to the polymer constituting the outer layer, the polymer, crystal nucleating agent, and other additives obtained by the polymerization are stirred with a Henchel mixer, brabender, or the like. The composition can be obtained by melt-blending at 180 ° C. to 280 ° C. using an extruder, and this can be used as a material for the outer layer. The crystal nucleating agent and other additives may be added using a linked extruder after undergoing polymerization, residual monomer removal, and drying steps. Further, a so-called masterbatch in which a high-concentration crystal nucleating agent is melt-kneaded with polyolefin may be mixed in a molding step of a polyolefin multilayer sheet or the like.

Further, the polymer constituting the outer layer may contain one or more kinds of resins or rubbers other than the polyolefin resin as long as the effects of the present invention are not impaired. The content may be a known amount.

(2) Core layer The core layer may be composed of any polyolefin, but preferably contains a polypropylene composition containing the component (1) and the component (2). The component (1) is a propylene homopolymer, a propylene copolymer, or a blend of a propylene homopolymer and a propylene copolymer. The component (2) is an ethylene copolymer. The weight ratio of the component (1) to the component (2) is 60 to 90:40 to 10, preferably 65 to 85:35 to 15. If the amount of the component (2) exceeds the upper limit, the rigidity of the sheet or the like decreases, and if it is less than the lower limit, the cold impact resistance of the sheet or the like decreases.

(2-1) Ingredient (1)
The component (1) is a propylene homopolymer, a propylene copolymer, or a blend of a propylene homopolymer and a propylene copolymer. These can be in any weight ratio, but preferably a propylene copolymer containing a propylene homopolymer and a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin as the component (1). It is a blend with a coalescence, in which the weight ratio of the two is 10 to 97: 90 to 3, and the content of the copolymer in the blend is 3% by weight or less. That is, the content of the propylene homopolymer in the component (1) is 10 to 97% by weight. If the content is less than the lower limit, the rigidity is lowered, and if it exceeds the upper limit, the molding conditions for improving the balance between transparency, cold impact resistance, and rigidity are limited. From this viewpoint, the content of the propylene homopolymer is preferably 40 to 90% by weight. Further, the propylene copolymer is preferably a propylene random copolymer.

The comonomer content in the blend is 3% by weight or less. If the content exceeds the upper limit, the rigidity decreases. From this point of view, the content of comonomer is preferably 1.8% by weight or less. As one embodiment, the propylene homopolymer and the propylene copolymer having a comonomer content of 0.2 to 10% by weight are appropriately blended in the range of 40 to 95:60 to 5 (weight ratio). The content of the propylene homopolymer and the content of the comonomer can be achieved. Ethylene is preferred as the comonomer from the viewpoint of industrially inexpensive, stable distribution and easy availability.

(2-2) Ingredient (2)
The component (2) is an ethylene copolymer composed of a copolymer of ethylene and one or more kinds of C3 to C10-α-olefins. The ethylene content is 60 to 90% by weight, preferably 65 to 85% by weight. When the ethylene content exceeds the upper limit value, the cold impact resistance of the obtained sheet or the like is lowered, and when it is less than the lower limit value, the transparency of the sheet or the like is lowered. The α-olefin is an α-olefin of C3 to C10, but propylene or butene-1 is preferable from the viewpoint of industrially inexpensive and stable distribution and relatively easy availability.

(2-3) Additive The polypropylene composition may contain a crystal nucleating agent of 1.0 part by weight or less, preferably 0.3 parts by weight or less with respect to 100 parts by weight of the composition, but does not contain it. Is more preferable. When the amount of the crystal nucleating agent exceeds the upper limit, the effect of promoting the formation of crystal nuclei reaches a plateau, and the manufacturing cost simply increases, which is not realistic in the case of industrial mass production at low cost.

In addition, the polyolefins that make up the core layer include antioxidants, chlorine absorbers, heat stabilizers, light stabilizers, UV absorbers, internal lubricants, external lubricants, antiblocking agents, antistatic agents, and antifogging agents. Usually used for olefin polymers such as agents, flame retardants, dispersants, copper damage inhibitors, neutralizers, plasticizers, foaming agents, bubble inhibitors, crosslinkers, peroxides, oil spreads and other organic and inorganic pigments. Conventional additives used may be added. The addition amount of each additive may be a known amount.

When a crystal nucleating agent and other additives are added to the polyolefin constituting the core layer, the polymer, crystal nucleating agent, and other additives obtained by the polymerization are stirred with a Henshell mixer, brabender, or the like. , A composition is obtained by melt-blending at 180 ° C. to 280 ° C. using an extruder, and this can be used as a material for a core layer. The crystal nucleating agent and other additives may be added using a linked extruder after undergoing polymerization, residual monomer removal, and drying steps. Further, a so-called masterbatch in which a high-concentration crystal nucleating agent is melt-kneaded with polyolefin may be mixed in a molding step of a polyolefin multilayer sheet or the like.

(2-4) Characteristics [MFR]
The polypropylene composition preferably has an MFR of 1.0 to 10 g / 10 min. MFR is measured at 230 ° C. and a load of 2.16 kg. If the MFR exceeds the upper limit value, it is easy to draw down during molding, which makes it difficult to manufacture a sheet or the like, and if it is less than the lower limit value, the load during molding becomes large and it becomes difficult to manufacture a sheet or the like.

[XSIV]
The polypropylene composition preferably has 0.5-2.0 dl / g of XSIV. XSIV is the ultimate viscosity of the xylene-soluble component of the polypropylene composition at 25 ° C. The xylene-soluble component is a non-crystalline component, and XSIV is an index of the molecular weight of the component. The main component of the xylene-soluble component is derived from the component (2). XSIV in the composition is obtained by obtaining a component soluble in xylene at 25 ° C. and measuring the ultimate viscosity of the component by a conventional method. If the XSIV exceeds the upper limit value, the transparency of the obtained sheet or the like is lowered, and if it is less than the lower limit value, the production stability of the polypropylene composition is lowered.

[Phase structure]
The polypropylene composition preferably has a phase structure in which the component (2) is dispersed in the component (1). Whether or not the component (1) which is a matrix is a blend of a propylene homopolymer and a propylene copolymer can be confirmed by DSC. For example, it can be confirmed by performing DSC analysis according to the method described in paragraph 0037 of JP-A-2011-184686. Specifically, the melting curve by thermal analysis when the polypropylene composition used in the present invention is reheated after repeating heating and cooling a plurality of times so that the maximum heating temperature is sequentially lowered satisfies the following x to z. In the case, the component (1) is a blend of a propylene homopolymer and a propylene copolymer.
x) The melting peak temperature is 165 ° C. or higher.
y) The proportion of components that melt at 170 ° C or higher is 5% or higher.
z) The proportion of components that melt at 160 ° C or lower is 15% or more.

The polypropylene composition may contain one or more resins or rubbers other than the polyolefin resin as long as the effects of the present invention are not impaired. The content may be a known amount.

(2-5) Method for Producing Polypropylene Composition As described above, the component (1) can use a propylene homopolymer or a propylene copolymer as a single substance, but a propylene homopolymer and a propylene copolymer are blended. Can also be used. For convenience, the propylene homopolymer of the component (1) is referred to as "component (1h)", and the propylene copolymer is referred to as "component (1c)". The polypropylene composition comprising the component (1h), the component (1c), and the component (2) can be produced by any method. For example, it can be manufactured by the following method.

Method 1: A method of preparing and mixing a polymer of each component. For example, a method including a step of polymerizing the raw material monomers of the component (1h), the component (1c), and the component (2) to produce each polymer, and a step of mixing the three.

Method 2: A method of preparing and mixing a blend of the component (1) and a polymer of the component (2), respectively. For example, the raw material monomer of the other component is polymerized in the presence of the polymer of either the component (1h) or the component (1c) to obtain the other polymer, or the raw materials of the components (1h) and (1c) are obtained. A method comprising a step of polymerizing a monomer and mixing the two while producing each component polymer to obtain a blend of the component (1), and a step of mixing the blend with the polymer of the component (2).

Method 3: A step of polymerizing the raw material monomer of the component (2) to prepare a blend in the presence of the polymer of the component (1h), a step of polymerizing the raw material monomer of the component (1c) to obtain a polymer, and the above-mentioned step. A method comprising the steps of mixing the blend and the polymer.

Method 4: A method comprising polymerizing the raw material monomer of the component (2) in the presence of the polymer of the component (1c). For example, the following method can be mentioned.
Method 4-1: A step of polymerizing the raw material monomer of the component (2) to prepare a blend in the presence of the polymer of the component (1c), and a step of polymerizing the raw material monomer of the component (1h) to obtain a polymer. A method comprising the step of mixing the blend and the polymer.
Method 4-2: A step of polymerizing the raw material monomer of the component (2) in the presence of the polymer of the component (1c) to obtain Blend 1, the raw material of the component (2) in the presence of the polymer of the component (1h). A method comprising a step of polymerizing a monomer to obtain a blend 2 and a step of mixing the two.

Method 5: A method of polymerizing the raw material monomer of the component (2) in the presence of a blend of the component (1). For example, a method including a step of preparing a blend of the component (1) and a step of blending the three while polymerizing the raw material monomer of the component (2) in the presence of the blend.

Among these, as will be described later, method 4 or 5 is preferable from the viewpoint of dispersibility of the component (1c) and the component (2) containing a specific amount of comonomer. In particular, it is preferable to polymerize the raw material monomer of the component (2) in the presence of the polymer of the component (1c) as in Method 4, because a sheet having excellent transparency in low-temperature molding can be obtained. Further, in general, a polypropylene composition having a relatively large amount of the component (2) is often difficult to produce, but as in the method 3 or the method 4-2, the component (2) is present in the presence of the component (1h). When the raw material monomer is polymerized, the amount of the component (2) can be adjusted without making the production difficult, and there is an advantage that it is easy to balance the rigidity and the impact resistance when the sheet or the like is used. The mixing method of the polymer and the blend is not limited, but it is preferable to prepare powders or pellets of each component and mix them using a known mixer or extruder. The method for producing a blend in Methods 2 to 5 and the like can be carried out using, for example, a reactor having two or more reactors or a reactor having two or more polymerization regions. The catalyst used for the polymerization is not limited, and a known catalyst may be used. Blends produced by such a method are so-called polymerization blends. The details of the polymerization method will be described later.

(3) Intermediate layer The intermediate layer may contain any polymer as long as the effect of the present invention is not impaired. For example, a return material or the like obtained by recycling a sheet or the like consisting of three layers of the present invention can be used as an intermediate layer.

(4) Characteristics of Polyolefin Multilayer Sheet, etc. The polyolefin multilayer sheet, etc. of the present invention can have an ultrathin outer layer, and thus exerts various excellent effects due to this. For example, a three-layer sheet in which polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin described above is the outer layer and the polypropylene composition described above is the core layer is taken as an example. I will explain. Since the sheet has a core layer having a phase structure in which the component (2) is dispersed in the component (1), the cold impact resistance of the sheet is improved, but the external haze is increased. On the other hand, the outer layer has a small outer haze because it does not have irregularities on the surface because there are no components having greatly different melting points. That is, the core layer contributes to the cold impact resistance of the sheet or the like, and the outer layer contributes to the improvement of transparency. If the outer layer is thick, the cold impact resistance is lowered, but in the present invention, the outer layer is extremely thin, so that the cold impact resistance is not lowered. From the above, the polyolefin multilayer sheet exhibits excellent transparency and cold impact resistance.

1. 1. Preparation of polymer (1) Polymer for outer layer [Polymer A1]
The solid catalyst used for the polymerization was prepared by the method described in Example 1 of European Patent No. 674991. The solid catalyst is made by supporting Ti and diisobutylphthalate as an internal donor on MgCl ₂ by the method described in the above patent publication. The amount of the solid catalyst and triethylaluminum (TEAL) and cyclohexylmethyldimethoxysilane (CHMMS) such that the weight ratio of TEAL to the solid catalyst is 8 and the weight ratio of TEAL / CHMMS is 6.5 ° C. Was contacted for 5 minutes. The obtained catalyst system was prepolymerized by holding it in a suspended state in liquid propylene at 20 ° C. for 5 minutes.
After introducing the obtained prepolymer into a polymerization reactor, hydrogen and propylene are fed, the polymerization temperature and the hydrogen concentration are set to 75 ° C. and 0.113 mol%, respectively, and the pressure is adjusted to adjust the weight of propylene alone. Manufactured coalescing. To 100 parts by weight of the powder of the polymer, 0.5 part by weight of Millad NX8000J (nonitol type, manufactured by Milliken) was added as a crystal nucleating agent, and 0.2 part by weight of BASF B225 as an antioxidant and a neutralizing agent. As a result, 0.05 part by weight of calcium stearate manufactured by Tannan Chemical Co., Ltd. was added, and the mixture was stirred with a Henchel mixer for 1 minute and mixed. This mixture is extruded at a cylinder temperature of 230 ° C. using an NVC φ50 mm single-screw extruder manufactured by Nakatani Machinery Co., Ltd., the strands are cooled in water, and then cut with a pelletizer to obtain a pellet-shaped propylene resin composition to obtain a polymer. It was set to A1. Polymer A1 is a polypropylene composition containing a crystal nucleating agent. The Tm of the polymer was 166 ° C.

[Polymer A2]
Diisopropyldimethoxysilane (DIPMS) is used instead of cyclohexylmethyldimethoxysilane (CHMMS), the weight ratio of TEAL / DIPMS is 3.2, ethylene is fed in addition to hydrogen and propylene, the polymerization temperature is 75 ° C, and the hydrogen concentration. A propylene-ethylene copolymer was produced in the same manner as in the case of the polymer A1 except that the ratio was 0.12 mol% and the ethylene concentration was 0.45 mol%. The weight of the obtained polymer was the same as that of the polymer A1 except that 0.25 part by weight of Millad 3988 (sorbitol type, manufactured by Milliken) was added instead of Millad NX8000J as a crystal nucleating agent to 100 parts by weight of the powder. Combined A2 was obtained. Polymer A2 is a polypropylene composition containing a crystal nucleating agent. The Tm of the polymer was 153 ° C.

(2) Resin composition for core layer [Polymer B1]
A solid catalyst in which Ti and diisobutylphthalate as an internal donor were supported on MgCl ₂ was prepared by the method described in Example 5 of European Patent No. 728769. Next, using the solid catalyst, TEAL as the organoaluminum compound, and dicyclopentyldimethoxysilane (DCPMS) as the external electron donor compound, the weight ratio of TEAL to the solid catalyst is 20, and the weight ratio of TEAL / DCPMS is 10. The contact was carried out at 12 ° C. for 24 minutes in such an amount. The obtained catalyst system was prepolymerized by holding it in a suspended state in liquid propylene at 20 ° C. for 5 minutes. The obtained prepolymer is introduced into the first-stage polymerization reactor of a polymerization apparatus equipped with a two-stage polymerization reactor in series, propylene is fed, and a propylene homopolymer is produced in a liquid phase state of propylene. , An ethylene-butene-1 copolymer was produced in the second-stage gas phase polymerization reactor. During the polymerization, the temperature and pressure were adjusted, and hydrogen was used as a molecular weight adjusting agent.
The ratio of the polymerization temperature to the reactants was that the polymerization temperature and the hydrogen concentration were 70 ° C. and 0.05 mol% in the first stage reactor, respectively, and the polymerization temperature, H2 / C2 and C4 / in the second stage reactor. (C2 + C4) was 80 ° C., 0.22 molar ratio, and 0.52 molar ratio, respectively. Further, the residence time distributions of the first stage and the second stage were adjusted so that the amount of the copolymer component was 30% by weight. Polymer A1 except that 0.25 part by weight of Adecastab NA-71 (phosphate ester type, manufactured by ADEKA Co., Ltd.) was added to 100 parts by weight of the obtained polymer powder instead of Millad NX8000J as a crystal nucleating agent. The polymer B1 was obtained in the same manner as above. Polymer B1 is a polypropylene composition in which an ethylene-butene-1 copolymer is dispersed in a propylene homopolymer matrix and contains a crystal nucleating agent.
Table 1 summarizes the characteristics of the polymer.

2. 2. Manufacture of Polyolefin Multilayer Sheet A three-layer sheet (particularly referred to as "pre-secondary multi-layer sheet") is manufactured from the polymer using a T-die extruder (Souken Co., Ltd.) equipped with a two-kind three-layer feed block. It was evaluated by the method described later.
The T-die was a 300 mm coated hanger die and had a lip width of 1.5 mm. The screw configuration was as follows.
For core layer: Full flight screw (φ30 mm, L / D = 38, CR 2.75)
For outer layer: Full flight screw (φ25 mm, L / D = 25, CR 3.2)
The pre-secondary multilayer sheet obtained above was heated at 150 ° C. or 160 ° C. for 120 seconds and biaxially stretched using a Bruckner film stretching apparatus (KARO) to obtain an overall thickness of 0.2 to 0. A 4 mm three-layer sheet (particularly also referred to as a "sheet-like laminate" or a "secondary-processed sheet-like laminate") was obtained. The biaxial stretching was carried out assuming secondary processing such as vacuum forming, compressed air forming, and vacuum forming. The conditions and evaluation results are summarized in Table 2.

3. 3. Analysis and Evaluation (1) Ethylene content of each component in the polymer or polymer For samples dissolved in a mixed solvent of 1,2,4-trichlorobenzene / benzene dehydride, JM LA-400 manufactured by JEOL Ltd. (1) It was calculated from the values measured by the ¹³ C-NMR method using a ¹³ C resonance frequency (100 MHz).
(2) MFR
The measurement was performed under the conditions of a temperature of 230 ° C. and a load of 2.16 kg according to JIS K 7210-1.
(3) XSIV
2.5 g of the sample was placed in a flask containing 250 ml of o-xylene (solvent) and stirred for 30 minutes at 135 ° C. at 135 ° C. using a hot plate and a reflux device to completely dissolve the sample. .. The solution was then cooled at 25 ° C. for 1 hour. Filter the obtained solution using filter paper, collect 100 ml of the filtrate, transfer to an aluminum cup or the like, evaporate to dryness at 150 ° C while purging with nitrogen, and leave to stand at room temperature for 30 minutes to dissolve xylene. Got a minute. Using a Ubbelohde viscometer, the ultimate viscosity was measured in tetrahydronaphthalene at 135 ° C. for the xylene-soluble component to obtain XSIV (dl / g).

(4) Polymer Tm
The Tm of the polymer was measured by performing a second scan defined as described above using a diamond DSC manufactured by PerkinElmer.

(5) Cold impact resistance A multilayer sheet before secondary processing was used as a test piece for measurement. Using Hydroshot HITS-P10 manufactured by Shimadzu Corporation, a measurement test piece was placed on a support base with a hole with an inner diameter of 40 mmφ in a tank adjusted to -30 ° C, and fixed using a sample retainer with an inner diameter of 76 mmφ. After that, the test piece was hit with a striker having a hemispherical hitting surface and a diameter of 12.7 mmφ at an impact speed of 1 m / sec, and the puncture energy (J) was obtained according to JIS K7211-2. The average value of the puncture energy of each of the four measurement test pieces was taken as the surface impact strength.

(6) Transparency A pre-secondary multi-layer sheet and a post-secondary sheet-like laminate obtained as described above using HM-150 manufactured by Murakami Color Technology Laboratory Co., Ltd. in accordance with ISO 14782. Was used as a test piece and haze measurement was performed to evaluate the transparency. In order to eliminate the influence of surface irregularities, liquid paraffin (Liquid Paraffin Cat. No. 32033-00, manufactured by Kanto Chemical Co., Inc.) was applied to both sides of the test piece with a brush, and haze measurement was performed in the same manner. The former was defined as "all haze" and the latter as "internal haze". We also defined "external haze"("allhaze"-"internalhaze") to see the contribution of the surface.

(7) Thickness For the multi-layer sheet before secondary processing, divide it into 5 equal parts at equal intervals in the width direction, cut out the central part of each into 3 cm x 3 cm, use it as a test piece, and measure the average value with a thickness gauge. The overall thickness. Furthermore, after cutting the cross section of the test piece with a microtome, observe the outer layers on both the front and back sides with a polarizing microscope with a magnification of 100 times, measure the thickness of the outer layers on both the front and back sides of the micrograph with a caliper, and use a standard scale. Converted to the actual thickness. The average value of the measured values of 10 points of thickness on both the front and back sides of the five test pieces was taken as the thickness of the outer layer. In addition, the standard deviation of the thickness of the outer layer was obtained from the measurements at 10 points. Regarding the sheet-like laminate after secondary processing used for the above transparency evaluation, the average value obtained by measuring the transparency measurement position with a thickness gauge is taken as the overall thickness, and the outer layer of the sheet-like laminate after secondary processing is used. The thickness was calculated from the following.
(Overall thickness of sheet-like laminate after secondary processing) x (Thickness of outer layer of multilayer sheet before secondary processing) / (Thickness of entire multilayer sheet before secondary processing)

In Examples 1 to 6 shown in Table 2, even when the thickness of the outer layer was thin, it became uniform, and a polyolefin multilayer sheet having a balance between cold impact resistance and transparency could be formed. On the other hand, in Comparative Example 1, the variation in the thickness of the outer layer increased in the width direction of the sheet, and the obtained sheet showed poor appearance as gloss unevenness as a whole, and the external haze was large and the transparency was deteriorated. Further, although an attempt was made to set the rotation speed of the outer layer cylinder to be more than 8 rpm and less than 30 rpm, the uneven gloss of the multi-layer sheet before the secondary processing and the deterioration of the external haze were not eliminated. In Comparative Example 2, the uneven gloss and the external haze of the multi-layer sheet before the secondary processing were eliminated, but the outer layer was thick and the cold impact resistance deteriorated. In Comparative Example 3, sheet molding could not be performed due to the torque increase of the extruder.
It is clear that the polyolefin multilayer sheet obtained by the production method of the present invention has an excellent balance between cold impact resistance and transparency.

1 Raw material resin inlet 2 Feed zone 3 Compression zone 4 Weighing zone

Claims (10)

Polypropylene multilayer sheet or film having an outer layer and a core layer and satisfying the following i) and ii):
i) The thickness of the outer layer is 1/40 to 1/100 of the total thickness and 2 to 50 μm. Ii) The core layer is thicker than the outer layer by the manufacturing method.
The steps comprising coextruding the outer layer and the core layer to form a polypropylene multilayer sheet or film satisfying i) and ii).
The extruder for forming the outer layer in the coextrusion step includes a feed zone and a compression zone from the upstream.
The temperature T (° C.) of the feed zone satisfies the relationship of the equation (1).
Tm-50 ° C ≤ T ≤ Tm-10 ° C ... (1)
(Tm is the melting point (° C) of the raw material polypropylene )
Production method. Further comprising a step of secondary processing the polypropylene multilayer sheet or film obtained in the coextrusion step so as to satisfy the above i) and ii).
The manufacturing method according to claim 1. The production method according to claim 1 or 2, wherein the outer layer contains polypropylene containing 0 to 5.0% by weight of a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin. Polypropylene composition with the following core layer:
As the component (1), it is a blend of a propylene homopolymer and a propylene copolymer containing a comonomer selected from the group consisting of ethylene and C4 to C10-α-olefin, and the weight ratio of the two is 10 to 97. : A blend of 90 to 3 and having a comonomer content of 3% by weight or less in the blend, and 60 to 90% by weight of ethylene as the component (2) and one or more kinds of C3 to C10-α-olefins. Includes an ethylene copolymer, which consists of a copolymer of
The following (i) to (iii) are provided. (I) The weight ratio of the component (1): component (2) is 60 to 90:40 to 10.
(Ii) MFR (230 ° C., load 2.16 kg) 1.0 to 10 g / 10 minutes (iii) XSIV (extreme viscosity of xylene soluble content) 0.5 to 2.0 dl / g,
The manufacturing method according to any one of claims 1 to 3. The manufacturing method according to claim 4, wherein the multilayer sheet or film includes three or more layers, and the outer layers are located on both outermost surfaces. The manufacturing method according to claim 5, wherein the multilayer sheet or film has a three-layer structure. The production method according to any one of claims 4 to 6, wherein the polypropylene composition has a phase structure in which the component (2) is dispersed in the component (1). The comonomer in the component (1) is ethylene, and the comonomer is ethylene.
The production method according to any one of claims 4 to 7, wherein the α-olefin in the component (2) is propylene or butene-1. The production method according to any one of claims 3 to 8, wherein the comonomer in polypropylene is ethylene. The production method according to any one of claims 1 to 9, wherein the T satisfies the relationship of Tm-40 ° C ≤ T ≤ Tm-20 ° C.

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